The ovarian follicular dynamics, vaginal electrical resistance (VER), progesterone (P4) and oestrogen (E2) profiles were investigated during the oestrous cycle in four indigenous ewes.
Material and Methods
Daily VER values were recorded with a heat detector. The follicles were observed and measured by trans-rectal ultrasonography. Blood was collected daily for hormonal profiles.
A significant variation in VER values (P < 0.05) in oestrus by ewes and position in the sequence of cycles was observed. Trans-rectal ultrasonography of ovaries revealed the presence of 2–4 waves of follicular growth. Study of hormonal profiles by ELISA revealed a positive correlation between E2 concentration and development of follicles and a negative correlation between P4 concentration and their development. The concentrations of oestradiol increased in oestrus and then decreased to a basal level. Follicular growth was accompanied by a rise in the concentration of serum oestradiol. Inversely, when follicles received the stimulation for ovulation, concentration of progesterone started to fall, but after ovulation, it climbed back to its peak and remained at this state until next ovulatory follicle reached its maximum diameter.
This study could help to set up a manipulative reproductive technique for improving genetic values in indigenous sheep.